Field of the Invention
The present invention relates to a zoom lens and an imaging apparatus. In particular, the present invention relates to a zoom lens used in an electronic camera, such as a digital camera, a camera for broadcasting, a camera for surveillance and a camera for film making, and also to an imaging apparatus including the zoom lens.
Description of the Related Art
A zoom lens used in an imaging apparatus, such as a video camera and an electronic still camera using imaging devices, such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor), as a recording medium, lenses are disclosed, for example, in Japanese Unexamined Patent Publication No. 9(1997)-218352 (Patent Document 1), Japanese Unexamined Patent Publication No. 2009-086437 (Patent Document 2), Japanese Unexamined Patent Publication No. 2010-185942 (Patent Document 3), and Japanese Unexamined Patent Publication No. 2007-017532 (Patent Document 4).
As high-definition digital cameras and high-definition cameras for film making became used in recent years, zoom lenses in which various aberrations are excellently corrected have become needed. Further, a request for a zoom lens with a small F-number FNo., which is a so-called bright zoom lens, has been increasing. Here, the request about FNo. is roughly classifiable into a request for a small FNo. at a wide angle end, a request for a small FNo. at a telephoto end, and a request for a constant FNo. with sufficient brightness from the wide angle end through the telephoto end. Further, when the zoom lens is used as a standard zoom lens, a full angle of view of about 70 degrees or greater at a wide angle end is requested. Recently, it is also desirable that the zoom lens has a hand shake blur correction function.
However, the zoom lens disclosed in Patent Document 1 has an FNo. of 4.6 through 7.2, which means the lens is not sufficiently bright. Meanwhile, the zoom lens disclosed in Example 7 of Patent Document 2 has an FNo. of 2.83 at a wide angle end, which means the lens is sufficiently bright. However, an FNo. at a telephoto end is 5.64, which is not sufficiently bright. Further, both of Patent Documents 1 and 2 are silent about hand shake blur correction.
In the zoom lens disclosed in Patent Document 3, hand shake blur correction is mentioned. Further, an FNo. at a wide angle end is 1.8 and an FNo. at a telephoto end is 3.5, which means the lens is sufficiently bright. However, a full angle of view at the wide angle end is 60 degrees, which means narrow. Therefore, the zoom lens is not appropriate for use as a standard zoom lens of a digital camera.
In the zoom lens disclosed in Patent Document 4, hand shake blur correction is also mentioned, and an FNo. at a wide angle end is 2.76, which is sufficiently bright. However, an FNo. at a telephoto end is 5.17, which is not sufficiently bright. Further, there is a problem that the total length of the lens is long, compared with the focal length at the wide angle end. Further, the refractive power of a lens group used to correct a hand shake blur is weak. Therefore, there is a problem that the movement amount of the lens group during hand shake blur correction is large.